More than 10,000 people each year in the United States have "failed back surgery syndrome" caused by scars that form around the outer surface of the spinal cord. Such scarring, known as peridural fibrosis, is common after back surgery known as either lumbar discectomy or laminectomy. Peridural fibrosis may cause recurring low back pain or leg pain after surgery. Operating again to remove the scar tissue often leads to more scarring.